The present invention relates to a liquid container for supplying a predetermined liquid to a liquid consuming apparatus, such as a liquid jet head, for jetting a minute amount of droplet, or the like and, more particularly, the technology to sense a residual amount of the liquid.
A liquid jet head of a commercial recording apparatus for super-high quality printing as well as liquid jet heads of a textile printing apparatus and a microdispenser receive a supply of a liquid from a liquid container. If the liquid jet head is operated without the supply of the liquid, the liquid jet head is damaged by the so-called blank shot. For this reason, a residual amount of the liquid in the liquid container must be monitored to prevent such damage.
Taking the recording apparatus as an example, various methods of sensing a residual ink amount in an ink cartridge serving as the liquid container have been proposed. JP-A-2001-146030 proposes that a vibration plate, to which a piezoelectric vibrator is fixed, is disposed contact the liquid. In this proposal, a frequency of a free oscillation of the vibration plate is sensed, which is changed depending on whether or not the liquid contacts the vibration plate.
However, in case where a space above the liquid is opened to communicate with the atmosphere for smooth supply of the liquid, the liquid is likely to be evaporated. Further, because the frequency is changed gradually as the liquid level in the area of the vibration plate is changed, a sensing accuracy is lowered.
JP-A-2004-136670 proposes a flexible bag containing the liquid therein and having: a liquid reservoir recess portion formed on one of opposing flat surfaces of the flexible bag; a piezoelectric vibrator disposed on an outer side of the recess portion; and a rigid body disposed on the other flat surface. In this proposal, a residual amount of the ink is sensed based on a vibration state that is changed depending on the liquid amount (a depth of the liquid) existing between the rigid body and the piezoelectric vibrator. This proposal can sense the remaining liquid amount with relatively high accuracy, but suffers from a problem in that sensing of the residual amount of the ink contained in the flexible bag is affected by deflection, crease, or the like of the flexible bag because the rigid body is moved to follow a deformation of the flexible bag,